Evidence is mounting that teenagers should start school a little later. So why aren’t they?

The medical community doesn’t fully understand why, but there’s something about puberty that throws kids’ systems out of whack. It’s as if teenage bodies switch over to daylight savings time, a condition sometimes known in the medical community as a “phase delay.” They begin to have trouble falling asleep early and then, of course, want to sleep in the morning for as long as possible. While teenagers may not need as much sleep as they did when they were children, their growing bodies still get pretty fatigued; they just don’t feel it until about two hours later.

“Why this happens nobody has a clue—hormone changes are a good bet,” says Dr. David Gozal, a pediatric sleep expert at the University of Chicago. “Paradoxically, this period of puberty is associated with an increased need for more and longer sleep. So now they’re in conflict with the sleep schedules of our society.”

That’s why advocacy groups, administrators and recently the American Academy of Pediatrics (AAP) have started to push for high schools to delay their start times so that students get more shuteye. In an August 2014 policy statement, the AAP said it supports middle and high schools adopting delayed start times (that is, no earlier than 8:30 a.m.) to allow teens to get the recommended hours of sleep a night (eight to 10), to improve their physical and mental health, safety, academic performance and quality of life. “[The] research indicates that the average teenager in today’s society has difficulty falling asleep before 11:00 p.m. and is best suited to wake at 8:00 a.m. or later,” the statement reads.

Data from a National Sleep Foundation poll shows 59% of kids in grades six through eight and a full 87% of high schoolers in the U.S. say they are getting less than the recommended amount of sleep. More than one in five of these students says he or she falls asleep while doing homework at least once a week.

With evidence suggesting that delaying the start of the school day can lead to more sleep, less reported fatigue and even improved academics, the switch seems like a no-brainer.The AAP recommends that schools should start at 8:30 a.m. or later, yet the most recent data from the U.S. Department of Education shows more than 80% of public schools in the U.S. start earlier than that. (And almost 10% start earlier than 7:30am).

“The evidence is clearly mounting in terms of understanding the repercussions that chronic sleep loss has on the health, safety, and performance of adolescents,” Dr. Judith Owens, director of sleep medicine at Boston Children’s Hospital and author of the AAP statement told TIME writer Alice Park in the book, The Science of Sleep. Some data suggests that anything under 8.5 to 9 hours of sleep on school days can contribute to health problems like obesity, mood changes and diabetes. Other data has linked poor sleep to a higher reliance on substances like caffeine, tobacco and alcohol. Not getting enough sleep can also take a toll on academic performance.

Sources: Sleep Foundation.org; sleep.org

“There’s also really compelling data supporting the fact that delaying school start times is a very important intervention that can mitigate some of the impact of sleep loss,” Owens tells TIME, suggesting if schools make the switch now, there’s time to prevent some of those negative outcomes. Even a half-hour delay, some studies showed, can have dramatic effects on improving children’s health and academic performance.

The research has caught the eye of some very influential educators. “It’s completely a local decision, but I’d like to see more school districts at least consider delaying start times,” says U.S. Secretary of Education Arne Duncan. “A later start to the school day could help boost students’ academic performance and reduce tardiness and absenteeism. Our commonsense tell us that sleepy students don’t do well in school, but the research also exists to back it up. Studies show that when students are rested, they are more alert and ready to learn.”

Intuitively, it makes sense. If teenagers are supposed to get up to 10 hours of sleep a night and get up for school at 6 a.m., that means many will have to be in bed by 8 p.m. or 9 p.m. Anyone who knows a teenager, or remembers what it was like to be one, knows that an 8:00 p.m. bedtime for a 16-year-old is laughably unrealistic. Not to mention that as entrance to highly regarded colleges gets more competitive, today’s teens keep incredibly busy schedules and trying to balance time for extracurriculars and homework can make it hard for them to fall asleep on time, and for their schools get everyone from parents to coaches on board to push back the start time.

Take Perrin Jones, a junior at Saratoga Springs High School in Saratoga Springs, New York. He wakes up every day at 5:30 a.m. to finish his homework and hops on the bus at 6:50 a.m. to make it to school for a 7:49 a.m. start time. Jones takes almost entirely all AP courses (he wants to get into a college like Carnegie Mellon or University of Michigan to major in physics and computer science), and he volunteers with the school’s IT department during the day. To keep up the schedule, he dropped lunch. After school he has at least one club meeting—he’s in the NASA club and the physics club—and at 6:30 p.m. he goes to the local theater where he’s on the sound crew. He gets home around 11 p.m., and then starts three hours of homework. He says he gets four hours of sleep on average, sometimes six on a good day.

“I don’t know how I keep going with such little sleep, but I do. I feel like I must learn how to survive without sleep to survive high school,” says Jones. “It sure would be nice if school started a little later, I’d definitely appreciate the extra sleep, even if it was half an hour.”

Trevor Weinrich, a senior at Rockhurst High School in Kansas City, Missouri keeps a similar schedule. From 5 a.m. to 7 a.m. he’s at swim practice. School starts at 8 a.m. and goes until 3 p.m., and he also skips lunch frequently for voice lessons. From 3:30 p.m. to 6 p.m. he has more swim practice followed by choir rehearsal. In the spring he was in three musical productions at once, and had rehearsals until 9:30 at night.

“My homework load averages about two to 2.5 hours a night. Many nights I eat dinner around nine or 10, and don’t get to bed until about 1 a.m or 2 a.m.,” he says.

While Weinrich and Jones are both ambitious students, the crowdedness of their schedules is not all that rare. It’s an issue many schools face—teens are overextended and too tired. So why have so few schools made the switch? Because it’s not as simple as it seems to persuade a whole community to change its schedule.

The Promise

Five years ago, Sharon High School in Sharon, Massachusetts decided to delay its start time after nearly eight months of deliberation. A task force of representatives from the school committee, the athletic department, teachers, parents, and students decided the school should move its start time back 40 minutes from 7:25 a.m. to 8:05 a.m.

“If [the change] was going to help them live a better life in some respects then it was the right decision to follow and that’s ultimately what we decided,” says Sharon High School Principal Jose Libano. “We will never go back. There is not a kid in this building who would say I prefer to be here at 7:15 in the morning. Not one.”

A year after the shift, the school polled its students, teachers and parents and found that parents and students largely felt the change was positive, while teachers were more split. The teachers felt they functioned better early in the morning, and they ran into commuting problems with the new start time. Still, there was a notable decline in tardiness, and teachers did say that since the change, students seem to be more alert and less lethargic during first period.

“They tend to be more active and willing to participate in discussion, volunteer to go to the board, or engage in group work, because they have gotten more sleep at night,” says Sharon High School Latin teacher Jen Orthman. “I think that despite some initial resistance to the change, most teachers appreciate having additional time in the morning to meet with students, collaborate with peers, partake in meetings, and set up classrooms for the day.”

Of course there was an adjustment period, as there tends to be with most schools that agree to push back their start times. Since community life can revolve around public school schedules, lots of factors—from sports games to when parks are open—need to be taken into account. Not to mention there’s often pushback from parents who are concerned about what impact the later time will have on their child’s after school schedule.

But other schools that have adopted similar changes have also noticed positive benefits. A three-year University of Minnesota study released in 2014 showed that high schools that started at 8:30 a.m. or later allowed 60% of their students to get at least eight hours of sleep each night. The teens who got less than that reported higher levels of depression symptoms, greater use of caffeine, and were at higher risk for making poor choices regarding substance use. Schools that started at 8:35 a.m. or later had better attendance and tardiness rates and better academic performance in core subject areas and in national achievement tests. The report also showed that the number of car crashes involving teen drivers was reduced by 70% when a school shifted start times from 7:35 a.m. to 8:55 a.m..

In Wake County, North Carolina, a study showed that delaying the start of school by one hour could lead to a two to three percentile point increase in math and reading test scores. The effect was greatest among students who were struggling.

When Glens Falls High School in New York first suggested pushing back its start time for the 2012-2013 school year, it met with a lot of opposition. Student athletes and their parents argued that their practices and games would end later, and therefore they would go to bed later too. The Board of Education was divided on the issue. The vote to implement the time change passed by a 5-4 margin in May 2011 and a motion to rescind the change failed by a margin of 4-5 in December 2011.

The school says it has seen improvements among its students since it required them to be at school later. The percentage of late students dropped around 3% from the 2011-2012 school year to the 2013-2014 school year. The number of students failing classes dropped 2.2% and the absentee rate dropped 1.5%.

It’s hard to draw a definitive line between later start times and better scores, mental health and safety, but many who are watching the experiments agree that the numbers showing teens get more sleep with a later start time are promising, given that more shuteye is the ultimate objective.

“Starting school later is in the best interest of your students,” says Libano, who is quite the evangelist for a later-starting day. “When there is a will there has got to be a way. It’s the right thing to do.”

The Challenge

While the evidence in support of letting students sleep in is intriguing, it’s an often-difficult feat to pull off.

“There were a lot of obstacles. It was divisive,” says Libano about the year the school pushed the new start time through. “It’s a topic that generates a lot of emotions because it’s a significant change.”

Significant may even be an understatement. Sharon High School was lucky; local buses were able to shift their pick-up and drop-off times without the school incurring additional costs. But the middle and grade schools had to change their start times too to accommodate the high school. Officials from Sharon had to go to the other schools in the district they compete against in extracurriculars and sports and ask them to plan competitions accordingly. Sharon also started regulating how long students could be held at practice after school. Ultimately the community was willing to adapt.

“It is very complicated to change a school or district schedule because community life revolves around school hours,”says Terra Ziporyn Snider, the co-founder and executive director of Start School Later, a non-profit working to persuade public schools to change their schedules. “It’s true even if you don’t have kids. Imposing a schedule change on an unwilling community is politically unpopular.”

The time schools start affects traffic flow, day care hours, small businesses that employ high school students, and when parks are open. While all that adjusting can cause some seriously ruffled feathers, Snider says if the change is done the right way, the whole community is involved in the implementation, and it comes off without a hitch.

Most of the time, according to Snider, people just don’t want to change the status quo. “The fear of the impact is incredibly powerful politically,” she says. “It’s fear of change and failure of imagination. It doesn’t mean that because you change the time you suddenly can’t have sports practice because school gets out an hour later. But people do think that and it stops change in its tracks.”

A common concern among critics of later school times is whether pushing back school will just mean that students get to sleep even later and will still be late for school. However, there’s evidence to suggest that’s not usually the case. A 2002 study of Minneapolis high school students showed that after the city’s school districts switched from a 7:15 a.m. start time to 8:40 a.m., kids in schools that switched had similar bedtimes to students whose schools didn’t change, resulting in one additional hour of sleep for the students. A 2010 study of a school that delayed its start time by 30 minutes showed average bedtimes actually shifted 18 minutes earlier, and average reported sleep duration increased 45 minutes. If teens are biologically programmed to go to sleep at a certain hour, pushing back a start time means they have more time in the morning when their bodies want to sleep in. And if their circadian clock is keeping them up at night, it’s not as big of deal.

“There’s zero evidence that the current hours are doing anyone any good and a lot of evidence that they are doing a lot of harm,” says Snider. “We are not talking about letting kids sleep in until 1pm every day, we are taking about letting them sleep until seven or eight in the morning. It’s not a very radical proposition.”

The Way Forward

For communities that want to take on the fight for a later start time, Snider recommends building an argument about sleep as the third pillar of health, after eating and exercise, an argument public health experts are increasingly promoting. Start School Later has 43 local chapters around the country that are available as a resource. Bringing in outside sources and advisors, say, from schools that have already taken on the challenge— can make the process much smoother, says Snider.

It’s hard to tell just how many schools have made a switch to a later start time, since some do so individually and others as a district, but interest is mounting. Libano fields many calls from schools inquiring about the change, and the U.S. Department of Education tells TIME that districts from Portland, Maine, to Ann Arbor, Michigan, to Durham, North Carolina, are looking at changing start times.

“While the decision of when to start school is up to the nation’s 15,000 school districts, the Department is interested in how innovative local efforts impact student achievement,” says Duncan. “School systems cannot carry on this work alone – parental involvement is critical to ensuring success for all students.”

In 2011, Fairfax County, Virginia, surveyed some of its 8th-, 10th– and 12th-graders to see how much sleep they were getting at night. The results showed that less than a quarter of high school seniors were sleeping seven or more hours. The data prompted the district to partner with the Children’s National Medical Center’s Division of Sleep Medicine to further study their students’ bedtime routines. Last year, the school board voted for a later school start. Come fall, students at the over 20 high schools in Fairfax County, who used to have to be at school at 7:20 a.m., can roll over and rest. High schools are now starting between 8:00 and 8:10 a.m., which is not exactly up to the AAP’s recommendation of 8:30, but it’s a start.